1. Field of the Invention
The invention relates to systems for controlling the level of a liquid in a vessel. More specifically, the invention relates to a system for controlling the level of the electrolytic solution in the pressure vessel of a hydrogen generator.
2. Description of the Prior Art
Liquid level control systems of the prior art have typically been characterized by conventional float and switch arrangements. Such arrangements are generally bulky and cumbersome and are not well adapted for use in relatively small, pressurized liquid containers such as the pressure vessel of a hydrogen generator.
The disadvantages of float and switch control systems have been recognized in the art. In U.S. Pat. No. 3,761,382, the pressure vessel of a hydrogen generator is provided with a single electrode probe which is adapted to detect the level of the electrolytic solution so that when such level drops below a predetermined point, a water pump is activated to replenish the liquid. This patented system is provided with a capacitive time delay which removes power from selected portions of the generator after a prolonged, unsatisfied demand for water.
The single probe technique of U.S. Pat. No. 3,761,382, although an improvement over previous practice, has proven to have several drawbacks in practice. First, the time delay shut-off system can shut down the system only after a prolonged period of low liquid level. In the time required for the time delay system to activate, the electrolyte level can drop below the partition separating the hydrogen and oxygen collection spaces and result in a mixing of these gases with a possible explosion. Furthermore, when the electrolyte level is below the top of the electrodes, the efficiency of the generator is reduced due to inadequate electrode exposure to the electrolyte and due to an increased concentration of caustic in the electrolytic solution. Thus, there is a need for a control system which will immediately shut down the entire generator unit when the electrolyte level drops below a predetermined danger level. A second drawback of the patented generator is that there is no reliable control means to prevent the liquid level from rising within the hydrogen collection space to a point where the liquid can be drawn into the hydrogen removal line. When the electrolytic solution is drawn into this line, there is extremely costly contamination of the line and the attached hydrogen purifier or other attached instruments. Thus, there is a need for means to prevent the electrolytic solution from entering the hydrogen removal line. A third drawback of the patented generator is that a single probe is not suitable for controlling the separate levels maintained within the hydrogen and oxygen collection spaces. There is a need for a multiple probe technique which will adequately maintain both liquid levels within a specified range.
Thus, it is a primary object of this invention to improve on the liquid level control system of U.S. Pat. No. 3,761,382 while maintaining the many advantages of such a system.